Spine surgery, such as vertebral fusions, is common and is becoming more reliable as better methods are developed for stabilizing the back and improving bone grafts, for example, to repair disc injuries, vertebral fractures, and the effects of osteoarthritis. Many spine surgeries require an anterior approach, such as those for degenerative disc disease (both de novo and to correct failed prior back surgery), for infected discs, tumor removal and scoliosis (e.g., for excision, drainage, or decompression).
Anterior fusions are often preferable to posterior fusions because the bone surface area available for the fusion is considerably larger and any discs to be removed are more accessible. This makes the likelihood of successful fusion greater and the time required for the operation less, translating to less time that the patient is under general anesthesia. For example, since the introduction of threaded devices for Anterior Lumbar Interbody Fusion (ALIF), this procedure has become quite popular in the treatment of degenerative disc disease and chronic spinal instability as well as in failed posterior arthrodesis attempts. The procedure, however, is heavily dependent on the ability of the approach surgeon to provide exposure quickly and safely in view of a reported incidence of vascular injury as high as 15% (Baker et al., Spine 1993; 18:2227-2230) and a 2.3% incidence of retrograde ejaculation (Regan et al., Spine 1999; 24:402-11). The requirement of a direct anterior-posterior exposure for alignment of the devices has presented a significant challenge to provide a small incision and yet maintain the degree of safety necessary to prevent injury to the iliac vessels and the autonomic nerve plexus.
Generally, there are two anterior approaches for clearing a surgical field for the anterior lumbar region currently in use. One is the paramedian rectus splitting anterior retroperitoneal approach and the other is the lateral muscle splitting retroperitoneal approach. Both of these approaches have the disadvantage that they damage the muscles through which the surgeon must go to access the retroperitoneal space. Damaged muscle can lead to increased analgesic requirements during recovery, hernias, and loss of muscle function in the patient. Additionally, these approaches may require a large incision, leading to increased trauma to the skin, abdominal muscles, and internal structures. This can increase the subsequent pain for the patient, which requires additional post-operative management, while increasing recovery time. Procedures that entail or result in penetration of the peritoneum also lead to increased risk to the patient, for example, through damage to peritoneal organs, subsequent adhesions, infection, and the like.
Likewise, many surgical instruments are used once the field has been cleared to allow the spine surgeon access to the lumbar region. Retractors are used to secure the area open during the spine surgery. A variety of retractors and blades, and other implements such as Steinman pins, have been used for this purpose (see, e.g., U.S. Pat. Nos. 3,998,217, 4,813,401, 5,025,780, 5,052,373, 5,688,223, 5,728,046, 5,795,291, 5,902,233, 5,944,658). While these retractors and implements help keep the area open and the tissue retracted, they suffer from several disadvantages. For example, standard retractor blades can slip out of place, or allow the peritoneum, peritoneal contents, nerves, vessels, or ureter to escape into the field of the surgery, risking injury to these structures. Hand-held retractors increase this risk. Pins are sometimes inserted into the vertebral body to hold back vessels and nerves, but they carry a great risk during deployment of the very damage the surgeon seeks to prevent. In lumbar region spine surgery, vascular injury, often perforation of the iliac vein and/or artery is the most common and severe complication. Other issues with the surgical instruments commonly used includes the size of the retractors, which may require a large incision in order to be placed correctly and to allow the spine surgeon a large enough field in which to work.
A need exists for an instrument and anterior retroperitoneal approach that permits rapid surgical access to the desired lumbar area, permits a small incision, and is stable and safe during subsequent procedures.